What are white holes?

October 9, 2015
by Fraser Cain, Universe Today

Black holes are created when stars die catastrophically in a supernova. So what in the universe is a white hole?

It's imagination day, and we're going to talk about fantasy creatures. Like unicorns, but even rarer. Like leprechauns, but even more fantastical!

Today, we're going to talk about white holes. Before we talk about white holes, let's talk about black holes. And before we talk about Black Holes, what's is this thing you have with holes exactly?

Black holes are places in the universe where matter and energy are compacted so densely together that their escape velocity is greater than the speed of light. We've done at least a million videos on them, but if you still want more info, you can start here with our Black Hole playlist.

Fully describing a black hole requires a lot of fancy math, but these are real objects in our universe. They were predicted by Einstein's theory of relativity, and actually discovered over the last few decades.

Black holes are created when stars, much more massive than our Sun, die catastrophically in a supernova.

So then what's a white hole? White holes are created when astrophysicists mathematically explore the environment around black holes, but pretend there's no mass within the event horizon. What happens when you have a black hole singularity with no mass?

White holes are completely theoretical mathematical concepts. In fact, if you do black hole mathematics for a living, I'm told, ignoring the mass of the singularity makes your life so much easier.

They're not things that actually exist. It's not like astronomers detected an unusual outburst of radiation and then developed hypothetical white hole models to explain them.

As my good friend and sometimes Guide to Space contributor, Dr. Brian Koberlein says, "If you start with five cupcakes and start giving them away, you eventually run out. At that point you can't give away any more. In this case you can't count down past zero. Sure, you can hand out slips of paper with "I O U ONE cupcake." written on them, but it would be ridiculous to use the existence of negative numbers to claim that "negative cupcakes" exist and can be handed out to people."

Now if white holes did exist, which they probably don't, they would behave like reverse black holes – just like the math predicts. Instead of pulling material inward, a white hole would blast material out into space like some kind of white chocolate fountain. So generous, these white holes and their chocolate.

One of the other implications of white hole math, is that they only theoretically exist as long as there isn't a single speck of matter within the event horizon. As soon as single atom of hydrogen drifted into the region, the whole thing would collapse. Even if white holes were created back at the beginning of the universe, they would have collapsed long ago, since our universe is already filled with stray matter.

That said, there are a few physicists out there who think white holes might be more than theoretical. Hal Haggard and Carlo Rovelli of Aix-Marseille University in France are working to explain what happens within black holes using a branch of theoretical physics called loop quantum gravity.

Artistic view of a radiating black hole. Credit: NASA

In theory, a black hole singularity would compress down until the smallest possible size predicted by physics. Then it would rebound as a white hole. But because of the severe time dilation effect around a black hole, this event would take billions of years for even the lowest mass ones to finally get around to popping.

If there were microscopic black holes created after the Big Bang, they might get around to decaying and exploding as white holes any day now. Except, according to Stephen Hawking, they would have already evaporated.

Another interesting idea put forth by physicists, is that a white hole might explain the Big Bang, since this is another situation where a tremendous amount of matter and energy spontaneously appeared.

In all likelihood, white holes are just fancy math. And since fancy math rarely survives contact with reality, white holes are probably just imaginary.

Astronomers using NASA's Chandra X-ray Observatory and the 6.5-meter Clay Telescope in Chile have identified the smallest supermassive black hole ever detected in the center of a galaxy, as described in our latest press release. ...

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docile

So much conjecture in this article it hurts my eyes. Black holes are mathematical constructs just like their white hole counterparts. You can ignore the constraints in reality.... like mass.... just like you can ignore the fact that you have to actually observe something to know it must be ubiquitous in the universe... like dark matter and gravitational waves. General Relativity has become nothing more than an appeal to authority buttressed by the infatuation with Einstein and blindness attributed to confirmational bias.

docile

docile

Zephyr:Small black holes which are evaporating via Hawking Radiation would actually glow white hot even if they weren't interacting with other matter.

If there are any around, we should be able to detect them directly. However, it would take eons and eons for a stellar mass black hole to evaporate down to say a planet-mass or mountain-mass black hole.

The smaller they are the faster they evaporate too.

Hawking has a formula that supposedly can calculate the rate of decay, but I honestly haven't looked at it in something like 15 years or so.

Ive always been kind of bothered about that explanation that an escape velocity > C means you cant escape. That doesnt seem quite right. You can for example escape earth's gravity at less than earth surface escape velocity. If you gain enough altitude - even at a very slow speed but with constant thrust - the escape velocity lowers until eventually it would be lower than your speed and you are good to go. Why then would that not work in a black hole? Can you not also have a positive vertical velocity within a black hole and eventually reach an altitude where escape velocity is less than C?

Adam, no you can not.Your idea works perfectly fine above the event horizon, but atoms themselves get ripped apart at that point.Imagine it this way, for the earth to become a black hole, it would have to be smashed into a ball less than a centimeter in diameter. That centimeter sized object would still have the mass of the earth.If you were in space you could be the same distance from that black hole as you are from the center of the earth right now and you would not feel any difference in gravity. The closer you got to it, the harder and harder it would pull you down until it was ripping atoms apart at its event horizon

Steve, your explanation seems to me to be totally different from the explanation often given that "you cant escape because escape velocity is > C". Is it related somehow or does your explanation imply that that other explanation is not really valid?

It should be quite hard to find a worst way to address such topic. Almost no info and a bunch of sentences for cranks to pick, quote and brag. Probably the worst article I've read in months.Courtesy of Fraser Cain, Universe Today.

docile

Since black hole surface area grows in direct proportion to things it consumes, there is no theoretical reason for white holes to exist. If the surface area remained constant, then there might be a reason. Also, if you agree with the idea of false quantum vacuum, there is no place for a white hole there, as energy states will be continually lowering over time.

docile

Good thing some of us can 'smell' propaganda as soon as even glanced at. We KNOW that no positive statements are gonna be in an article about a subject not 'physipolitically correkt' and we also KNOW what the 'taboo subjects' are. So when a 'teaser article' is seen, we automatically skip to the end and read the predictable last sentence: "Words like..bunkum...move on...nothing to see here" prettiy much describe the drivel that went before and tie it in a neat silly package for the foolish and apathetic and/or fearful or superstitious.

This piece of trash truly insults the intelligence of a dolt. Matter spewing out of a 'hole' that is not allowed to have any matter in it. Talk about half truths followed by parrotspeak.

Adam Russel,The radius of a black hole is equal to2Gm/c^2All that is defining is a region of space where the escape velocity is above the speed of light, and because everything is divided by c^2 (a pretty large number), all black holes have comparably large masses in respect to their radii.G is the gravitational constant, as defined by Newton, m is the mass of the object in question. The only number that you can change to impact the size of the black hole is mass, 2, c and G are unchanging constants.

The gravitational energy between two objects in Newtonian terms is:F=G((Mass1)(mass2))/r^2. F is the force, R is referring to the distance between the two objects, with G being the the gravitational constant.

For something to be a black hole, it must therefore have a small enough radius in order to generate enough force to prevent light from escaping. As defined by the equation, it weakens exponentially, so a black hole horizon must be very small.

Ok, to be more clear - I wasnt questioning whether you could escape from a black hole so much as the logic contained in the reasoning that "escape velocity is > C so you cant escape because you can never reach C".

One of the other implications of white hole math, is that they only theoretically exist as long as there isn't a single speck of matter within the event horizon. As soon as single atom of hydrogen drifted into the region, the whole thing would collapse.

Isn't that not allowed though? I was under the impression that the white hole has an anti-event-horizon, meaning that nothing can enter it.

What's mass? Oh yes, because Higgs. C and big G are constants.Says who?Sounds like wishful thinking to me. Hubris, hubris.You are all in good company. Newton had it. So did Lord Kelvin. Science is not a religion. Or at least it wasn't when I was a lad.We weren't allowed to pluck a statement out of the air, no matter how important it made us feel.

Ok, to be more clear - I wasnt questioning whether you could escape from a black hole so much as the logic contained in the reasoning that "escape velocity is > C so you cant escape because you can never reach C".

Adam, this is a little counter-intuitive, but the gravitational acceleration of a 1 solar mass black hole just above it's event horizon (about 2.9km radius) is 15 trillion m/s^2. Even if you were 10 times farther away initially, it wouldn't matter. Not even an ideal anti-matter rocket could escape that even from 10 radii away. You're screwed.

Isn't that not allowed though? I was under the impression that the white hole has an anti-event-horizon, meaning that nothing can enter it.

I believe a true white hold would eventually become a black hole; a white hole horizon nested inside a black hole horizon, due to the accumulation of matter and energy outside the white hole horizon.

Suck a structure would essentially be a pocket universe.

Some of the larger supermassive black holes are very difficult to explain through galaxy mergers and dark matter capture alone. I've done the math and the total average dark matter (if it even exists) which would be captured by a supermassive black hole during the age of the universe is actually an insignificant fraction of the actual masses observed in the largest supermassive black holes.

This suggests some other...bigger...mechanism for growing super massive black holes...unless those 15-20G.M. Black Holes just literally swallowed every start in a dwarf galaxy.

So the largest known supermassive black hole has an estimated mass of about one tenth that of the entire milky way galaxy (this value has been revised down to around 200 billion suns due to more recent, more professional work done using globular cluster orbits...down from the vastly over-inflated 1 trillion suns you will find in physics texts an wikipedia encyclopedia. The article was on physorg, so if some troll like otto demands a reference, screw you. Look it up for yourself.)

So...Either these SMBH ate literally every star in an entire dwarf galaxy...or something else happened which makes them this big.

Another thing, recently some galaxies have been found to have even larger SMBH, relative to their total galactic mass, than previously predicted.

Maybe at the creation event, some regions of space time were just that much denser with matter? Is that all we need to explain these behemoth SMBH and such? Instant catastrophic gravitational collapse?

For something to be a black hole, it must therefore have a small enough radius in order to generate enough force to prevent light from escaping. As defined by the equation, it weakens exponentially, so a black hole horizon must be very small.

......the so-called Event Horizon is the actual surface of the BH. This is simply because the surface of the BH is the area where gravity is at its maximum thus preventing Electro-magnetic energy from reaching Escape Velocity of light-speed. Any distance beyond the surface is no different with regard to Escape Velocity even if it is only a fraction of an inch.

Soem fission, but these mostly originate with the fusion of hydrogen as well...

What about the first matter in teh universe? What percent of the first particles created in the universe were neutrons? And having no electric charge and weaker interaction with EM than the proton or electron, where did they go and to what were they attracted?

When I said DM would make up an insignificant fraction of a SMBH mass, that was based on the amount of DM that a SMBH would be likely to run head-on into as it's host galaxy plows through space during the 13.7 billion year age of the universe, using average density of supposed DM particles as an estimate. It doesn't take into account capture of any DM which somehow gets "de-orbitted" from halos due to interactions between globular clusters or close-encounters with other galaxies, because there is no way to estimate how much material that would be nor how often that would happen.

Further, due to some other issues, such as the true N-body solution to gravitational acceleration, the more of the host galaxy which is consumed by the black hole, the less total gravitational acceleration is felt by an object passing near the edge of the host galaxy. Inverse square law causes this, because a star close to a planet has more effect than a SMBH 100kly distant.

But if the SMBH eats the star somehow (it got sling-shotted around by another star), then the mass of that is now 100k ly farther away from the other passing object (outside the galaxy) so the total net acceleration on the object does in fact go down.

You might say "aha, but on average a star from the other side of hte galaxy might get consumed too".

Yeah, but I've done the math on how that works, and due to inverse square law, the effects of the star 200k ly distant from our passing object (or 100k ly if it is eaten) is still insignificant compared to the effects of our 1 star a few ly distant on the outside of the galaxy.

To put this in perspective, the Large Magellanic cloud, one of the largest systems you can see with naked eye or small telescope, is believed to have a mass of 10 billion Suns. This is slightly less than half the mass of the most massive estimated Super Massive Black Hole.

I am waiting for the first discovery of a 100 billion mass black hole, and then a 1 trillion mass black hole.

They are probably out there somewhere, having gouged out a galaxy-sized or galaxy cluster sized "void" in space.

For something to be a black hole, it must therefore have a small enough radius in order to generate enough force to prevent light from escaping. As defined by the equation, it weakens exponentially, so a black hole horizon must be very small.

......and any point above the surface is where this weakening must occur in accordance with the Inverse Square Law as applied to gravity.

Egleton.The force of gravity and the speed have been MEASURED to be the same strength they are now as they spread have to within parts per billion.If you don't believe they are constants, you must suggest a mechanism that would change them, and how you could measure that change

Ok, to be more clear - I wasnt questioning whether you could escape from a black hole so much as the logic contained in the reasoning that "escape velocity is > C so you cant escape because you can never reach C".

Adam, this is a little counter-intuitive, but the gravitational acceleration of a 1 solar mass black hole just above it's event horizon (about 2.9km radius) is 15 trillion m/s^2. Even if you were 10 times farther away initially, it wouldn't matter. Not even an ideal anti-matter rocket could escape that even from 10 radii away. You're screwed.

If you are saying that within the black hole EH it is not possible to have a positive vertical velocity because gravity is too strong then I could see that explanation. But that kind of makes the previous explanation (that I have been questioning) meaningless. Why say you cannot reach escape velocity because it is beyond C when in fact you cannot even attain a positive vertical velocity at all?

Exactly what I was thinking Bongstar 420. Although it wouldn't solve the "something from nothing" beginning of the Big Bang, it would kick the issue down the road a notch. As for the question of how life could begin and survive in such an environment, well, I don't know of any proven physics from within a black hole. Our point of reference being the only one we currently have available.

docile

adam: the simplest way to look at black holes is to consider that the physics inside the Event Horizon is THEORETICALLY unmeasurable. That makes any discussion of it as valid as discussing the number of Angels which can dance on the head of a pin. Feel free to discuss it, but keep in mind its as valid as astrology, numerology, and the galactic alignment. The physics outside the EH is, in very simple (theoretical) cases, well established...But you need to keep in mind that despite Fraiser's incorrect claim that they have been "discovered", all we have is the observation of areas of space, far far distant from us, which seem to behave AS IF that area is near a massive object with an event horizon, at least according to our models of what that behavior would be. There is some interesting physics going on in these areas of space, and we do NOT have a better (or even an "almost as good") explanation for what these areas surround, so the consensus is they surround black holes.

The value of any one post on Phys.org is proportional to exp(-A*(N-1)) where A >>1 and N is the total number of posts on that thread by the same author. FWIW. So, for this, for me, N=2. There is no known physical process which would allow the EH to be crossed in a finite amount of time. That is, the claims that things "fall in" to a BH is shorthand (or just wrong) for the fact that according to the math, an object will pass through the EH at time = +∞. Let me know after you've observed that! Also, due to red-shift, the frequency of any light/radiation coming from the EH is 1 ÷ ∞. Hence, it is black. There's a bunch of interesting physics near a black hole, but your questions about inside a black hole must assume that our physics, which we know is NOT right in very very high gravity, is right in very very high gravity. Discussions about what happens "inside" is really a discussion about how our models extrapolate past the EH. Might as well debate religion